Will Johnson and I, after months of talk, finally made it to the
"Grotto," a small basalt area near Jamestown.  I got a copy of the
2 page map/guide from Ken Sims, so we had no trouble finding the
place.  Driving time is about 2 1/4 hours from Berkeley, about the
same as the Pinnacles.  The last 1.5 miles of the drive are on a rutted
dirt road, but Will's little Toyota splashed through the puddles
just like a 4WD commercial.  The cliff is on the N side of the
long basalt formation (Table Mountain) that you see on the left
side of 120 on the way to Yosemite.  The cliff band is several
miles long, but most of it looks like choss.  The areas is infested
with poison oak, but the locals have blazed a nice trail (10 minute
walk) up to to the wall.  The big surprise is that, in the middle of
all this bad rock, the wall drops down into a, well, grotto, with
about 50' of pristine hexagonal columns on the main wall, and two
short overhanging walls (ca. 30') opposite, forming a sort of 
triangle.  Basically, there are crack climbs between columns, and
sport routes on the short walls and on the headwall above the
columns.  There are about 20 routes (5.8 to 5.12), all within a
few steps of each other.  Will and I ticked quite a few routes - I'll
just summarize with a brief comment.

Cracks:

Three Finger Jack (10d, 40') - JA led, WJ followed.  Sharp, more like 10b 
Snake Bite (11, 40') - JA TR; about 11a.  Will's fingers didn't fit.
Rawhide (11a, 45') - JA led, WJ followed.  Sinker fingers, painful.
Go with the Flow (10a, 50') - approach to some of the upper wall routes, 
   about 5.8.  JA led

Sport Routes:

Chicken Ranch Bingo (10c, 70', ca. 10x) - JA RP, WJ PP.  Slightly overhanging
   jug fest.  An excellent warmup and the only easy route on the upper 
   headwall.  10a or 10b.

Clip, Clip, Wow (10+, 35', 5x) - JA RP, WJ PP. best route on the short wall.
   10d.
Geronimo (11, 5x) Will and I both worked this, it was a little muddy.  11b/c.
Color Coded Quick Draws (10c, 5x).  WP RP, JA PP.  More jugs.
Side Saddle (5.9, 4x)  WJ RP, JA PP.  Still more jugs.

A.C. Devil Dog (11a, 4x, 60') WJ RP, JA follow.  Cool route on the face 
  between two columns with laybacking of both aretes.  10d.
Unnamed headwall route (?????)  I guess this is what I deserved for
  downrating all the crack climbs in front of the locals - on the other
  hand I knew it could not be "10+"  Nice rock and bolts, though.

What a day!  We even met one of the locals and got to thank him for the
trail and the nice bolts.  Other parts of the cliff are under development,
with trail construction and scrubbing projects ongoing.  He mentioned that
he had never seen so many parties in the Grotto - four.

Joel

Topo available upon request.  It is also available at Sonora Mountaineering.